Apparatuses and methods for measuring the audience of a media presentation, such as a television or a radio programme, are well-known in the industry. The knowledge of the size and composition of audiences to television or radio broadcasts associated to certain environments, for example in a home, is of paramount importance for the broadcasting industry in order to value the advertising space included in broadcasts.
The group of viewers cooperating in a television audience survey is called a “panel”, while each viewer participating in the panel is called a “panel member”. Audience metering apparatuses cooperate with associated media rendering devices or display systems used by panel members for watching television broadcasts at their respective viewing locations. Such metering apparatuses have three main goals, namely: a) determining the content being shown on their associated media devices; b) identifying the broadcast source (e.g. television channel or other audio or video broadcast stream) and the content distribution platform (e.g., analogue terrestrial transmission, digital terrestrial transmission, analogue satellite transmission, cable TV, IPTV, etc.); and c) registering the presence of one or more panel members so that the exposure to the content, broadcast source and platform can be accounted for, so as to produce audience data.
Audience metering systems typically include a set-top box connected to the media device (traditionally a TV set). In order to identify the content, broadcast source and the platform of the viewed programme, these metering systems may use one or more different methods available, such as tuner frequency measurement, or recognition of embedded video or audio codes, Service Information, image feature recognition, watermarking, and signatures, amongst others.
In the case of the signature recognition, many systems have been proposed which, essentially, include a metering device that derives signatures continuously either from the audio or video output (or both simultaneously) of the TV set or display device, and store the signatures together with an associated time stamp. The stored signatures generated by the metering devices are later transmitted by modem or any other telecommunications means to a remotely located central base (or station), where they are processed in order to identify all content shown on the monitored TV set or display device
This function may be achieved by means of content identification technology comprising a set of techniques and methods that can recognize an unknown segment of audio or video material among a plurality of reference segments generated from known broadcast sources. Persons skilled in the art will acknowledge the existence of methods and algorithms used for content identification by means of the generation and recognition of signatures. Audio and/or video signals are converted into signatures that characterize the media content being analyzed. A pattern correlation engine is then used to identify an unknown piece of content by scanning its signatures against a large set of previously-generated reference signatures. The content being displayed is then determined by analyzing correlation values according to appropriate algorithms in order to provide a wide range of media measurement and monitoring services, of which the most widely used is “Broadcast Identification” (i.e. recognizing a broadcast source being watched on a TV set; in the case of television audience measurement, for example, the broadcast source is typically a television channel).
It may happen, however, that two or more different broadcast sources comprise identical content during certain periods of time. This type of event is known as simulcast transmission, and is characterized by the fact that the scanning engine will find two or more reference signatures matching the signature of the unknown piece of content, generating an ambiguous situation in which the audience measurement system cannot unequivocally assign the content to one broadcast source.
In the case of content matching systems coupled with a source detection metering system, such as the one proposed by Wheeler et al. (U.S. Pat. No. 6,675,383), an approach has been implemented to solve the problem. If the audience metering device can identify the broadcast platform associated to the source providing the signal to the TV set or media rendering device during the simulcast period, the scanning process considers only the reference matching signatures originated on broadcast sources transmitted in the identified platform. This can eventually reduce or even eliminate the ambiguity, except for the case in which the simulcast involves two or more broadcast sources transmitted on the same platform (e.g., two analogue terrestrial channels or two digital satellite channels).
Another approach involves the detection of auxiliary codes or any other type of metadata present in the broadcast signal that could eventually identify the content and/or broadcast source viewed by the panel member(s), as proposed, for example, by Neuhauser et al. (International Patent Publication No. 2004/062282), where audio data is identified based on both a signature characterizing the audio data and additional data obtained from the audio data (as, for example, a source identification code). However, people skilled in the art know that if the codes or metadata are present in the broadcasting signals received by the panel members, code detection is used as the main audience measurement method, and the generation of signatures is usually implemented as a second option when the codes or the metadata streams are not detectable or not present, as proposed by Thomas et al. in U.S. Pat. No. 5,481,294, which describes a household metering apparatus which records ancillary codes or extracts programme signatures from the programs if no ancillary codes are found in the broadcast signal. As a general rule, content matching methods are used when the audience measurement system cannot rely upon the full availability of codes or metadata.
A third approach, as suggested by Williams et al. in U.S. Pat. No. 5,945,988, may involve the use of known audience data from the monitored panel member(s) in order to enhance the identification of an audio sample. This solution, however, can only provide a best guess based on historical data.
Finally, the case of simulcast transmission has been addressed by Lee et al. and described in International Patent Publication No. 2005/006768. However, the solution described therein is for the specific case wherein the signatures are generated based on a Cycle Redundancy Check (CRC) or recognition of other predetermined data packet portions of a digital broadcast signal. This method, therefore, cannot solve the problem in the case of analogue broadcast signals, or in the case of audience measurement systems that generate signatures based on time-domain or frequency-domain features of a digital audio or video signal, which might be received remotely having been transmitted through the air from a presenting device (such as a television) as an audio wave or as an electromagnetic wave.
There is, therefore, a need to solve the problem faced by content matching technologies in simulcast cases where complementary information provided from a platform detector is not available or is not sufficient to identify a broadcast source, or broadcast source recognition by means of auxiliary codes or other type of metadata is not feasible.